Problems associated with vehicles having lift mechanisms which collide with overhead obstructions have become increasingly prevalent in recent years. There are many reasons for this, including increased truck traffic, drivers who are unfamiliar with the operating environment of their vehicles, and the deterioration of highway infrastructures due to reduced budgetary allocations.
U.S. Pat. No. 5,389,912, entitled TRUCK CLEARANCE ANTI-COLLISION DEVICE, provides a useful background associated with the problem of tractor-trailer type semi-trucks coming in contact with overhead obstructions such as bridges, and so forth. As a solution to this problem, this patent proposes a vehicle clearance anti-collision device which includes an ultrasonic transmitter and receiver for receiving signals reflected off of an object disposed vertically above the cab portion of the vehicle. An on-board computer operatively associated with the transmitter and receiver automatically calculates the vertical distance between the height of the truck and the object being approached, and provides to an operator information as to the available clearance.
There are many potential problems associated with systems of the kind just described. Firstly, in the event that the vehicle is traveling at high speed, despite the warning provided by the transmitter/receiver, notification to an operator may come too late. Secondly, by virtue of the ultrasonic transducers involved, in conjunction with the computer automation and operator indicators, such a system may be too expensive for all but the most precious vehicles or cargo. In addition, this patent, and others like it, do not address the particular needs of vehicles having vertical extensible but retractable apparatus in the form of dump boxes, booms, lift buckets and fork lifts, which may only present a hazard with respect to overhead objects when the apparatus is in its extended position. That is, with the apparatus retracted, collision may inherently be avoided. Accordingly, there remains a need for a simple solution to collision avoidance in the case of vehicles having such vertically extensible/retractable apparatus.